The overall objective of this project is to extend the applications of optical spectroscopic methods, especially circular dichroism (CD), in the study of macromolecular structure and function. Contributions of the peptide background will be studied theoretically. Small linear peptides will be studied as models for the unordered and beta-turn regions of protein chains. The CD properties of beta-bulges will be evaluated theoretically. Also, the effect of twisting beta-sheets and of the interaction of adjacent elements of secondary structure will be analyzed. The CD contributions of side-chain chromophores will be examined theoretically and experimentally. Nearest-neighbor interactions involving tryptophan and histidine side chains with adjacent peptide groups will be calculated. Calculations will also be performed to evaluate the total CD aromatic side chains in several small well-characterized proteins such as ribonuclease and lysozyme. Aromatic CD contributions in the far ultraviolet will be evaluated experimentally using fluorescence detected CD (FDCD). The interaction of heme groups in multiheme proteins will be studied theoretically and experimentally. Experimental work will also be carried out on reconstituted myoglobins to test the effect of porphyrin substituents and metal atom on the CD. Mutant human hemoglobins and various species will also be studied experimentally. The origin of the CD and the spectral shifts of NADH bound to dehydrogenases will be studied theoretically. The source of induced CD in flavoproteins will also be examined. Studies of triphenylmethyl dyes binding to various nucleotide-binding proteins will be pursued. The potential of triplet-triplet transitions as CD probes will be examined. Etheno derivatives of ATP and NADH will be used as FDCD probes of kinase and dehydrogenases, respectively. The origin of induced CD in complexes of antibiotics with nucleic acids will be explored.